The invention relates in general to electronic packaging and in particular to thermal shielding for electronic components.
Lifecycle sustainability and reliability are key requirements for gun launched munitions. Due to the long storage shelf life and wide range of operational conditions experienced, gun launched munitions are expected to maintain functionality in a large thermal environmental range. For example, over its operational lifetime, a typical gun launched munition may experience storage environments ranging from arctic conditions to desert conditions and be exposed to temperatures reaching 400° F. Accordingly, such munitions are tested in thermal extremes to ensure lifecycle sustainability and reliability. The current storage requirement thermal range for gun launched munitions is from −50° C. to 71° C.
Electronic components and other thermally sensitive components exposed to thermal shock (i.e. extreme thermal gradients) can experience low reliability and failures. For example, these failures may be heat aging, structural overloading induced by thermal expansion mismatch (between component, potting and solder), swelling/contraction of component, joint fatigue and failure, cracking in components and diminished electrical components.
Ceramics are known thermally resistant materials. Current thermal barrier oxide materials are primarily employed in industries where metallic components are exposed to high heat thermal cycling (i.e. >1100° C.). Because of this, most commercial thermal barrier oxides are processed and operated at extremely high temperatures to obtain and maintain stable oxide phases. Heat shields or thermal shields such as traditional thermal barrier oxides are processed via physical or chemical vapor deposition, thermal spray or plasma spray coating techniques.
There are disadvantages to the above processes for developing thermal barrier oxides and heat shields from traditional materials for gun launched electronics applications. Primarily, the high temperature deposition processes required to ensure adhesion to the substrate fall outside the thermal tolerance range of many electronics components. Additionally, the current thermal barrier oxide systems are unstable in the operating range of munition electronics components and thus may not adequately function as a thermal shield potentially yielding similar physical and functional failures of electronics components observed during thermal cycling and thermal shock. Finally, the adhesion quality between current thermal oxide shields and non-metallic components is questionable.
Currently, potting materials may be used for some thermal insulation for an electronics component. However, potting is known to exhibit unstable material properties with thermal variances. Additionally, thermal mismatch between the potting and the ceramic component lends itself to potential hardware failures.
A need exists for a thermal shield which protects electronic components, such as those used in a gun launched munition, from the effects of thermal shock.